I always have a cribbage board and a deck of cards around. It's a laugh out loud riot to teach new players over a couple of beers. Cribbage is a great background game to sitting around and shooting the shit.
Same with having a guitar or two around. Bunch of great songs can get people humming and singing and beating on buckets etc.
When there were more kids around I gave my kid a deck of Bird ID cards...lay 'em all out face down, then the players take turns turning one over and guessing where it's match is, like the old Concentration game. When they got a match they kept both cards. Player with the most sets wins.
Each card had facts about the bird pictured; name, size, range, habits, etc. Those kids remember their bird facts to this day and still give each other bird ID related gifts for birthdays and xmas.
We also did tree, plant, and animal track ID activities, though not with cards.
Lastly, we'd make up stories together with mythical elements, with a protagonist, a challenge, refusal, mentor, etc about places like Emerald Island (a large mound in the middle of a field with pines on it), Pierce's Pond, Buzzer the Cross-Eyed Bumblebee, etc.